1. Field of the Invention
The present invention relates to a method for processing silver halide photographic materials and, more particularly, to a processing method for silver halide photographic materials having high suitability for rapid processing which ensures reduction in silver stain (or silver sludge) and color stain.
2. Prior Art
The graphic arts industry is strongly desirous of an improvement in operating efficiency and an increase in operation speed. Accordingly, there are comprehensive needs for the scanning operation to be speeded up and for the processing time of a photosensitive material to be shortened.
In order to meet these needs in the graphic arts, it is desirable for an exposure apparatus (including a scanner and a plotter) to increase its scanning speed, and further not only to increase the number of its scanning lines but also to converge its scanning beams with intention of enhancing the image quality. On the other hand, it is desirable for a silver halide photographic material to have high sensitivity, high stability and high suitability for rapid photographic processing.
The term "rapid photographic processing" as used herein refers to the processing in which it takes 15 to 100 seconds for the top of a photographic film to travel from the insertion slit of an automatic developing machine to the exit of the drying part of the machine via the developing tank, the transit part, the fixing tank, the transit part, the washing tank and the drying part in succession.
In order to render a photographic material suitable for rapid processing and to effect the rapid photographic processing thereof, it is necessary to increase a developing speed and a fixing speed and to shorten a drying time. As a means for achieving such purposes, it is effective to reduce the contents of gelatin used as a binder in emulsion layers and protective layers. In particular, reduction in thickness of protective layers is required. As a result, the photographic material faces a serious pressure-fog problem.
As a means for lessening the density change caused by pressure, it is known to adopt, e.g., the method of adding a polymer latex or a plasticizer such as a polyhydric alcohol, the method of reducing a silver halide/gelatin ratio in the silver halide emulsion layer, the method of increasing the thickness of a protective layer or the method of adding a lubricant or colloidal silica to a protective layer for the purpose of lightening the pressure before it reaches silver halide grains.
However, the addition of a plasticizer is restricted in the amount used since it lowers the mechanical strength of the emulsion layer, while the reduction of the silver halide/gelatin ratio and the increase in thickness of the protective layer retard the progress of development to impair the rapid-processing suitability of the photographic material. Further, the addition of colloidal silica or the like to a protective layer is insufficient onto the prevention of the change in image density due to pressure.
In addition, it is also effective to increase the amount of a hardener added to a silver halide photographic material. According to this method, the photographic material can have improved resistance to damage by pressure because its swelling degree in a developer can be reduced, but it suffers from an increase of color stain.
On the other hand, resources, produced gases, waste water, other various wastes and so on, have been reinspected in many fields from the standpoint of environmental preservation. In the field of photographic processing, there are growing needs for reduction in replenishment rates of processing solutions used for processing photographic materials in view of saving resources, reduction in amount of waste water, reduction in volume of vessels used, and so on.
However, reduction in replenishment rate of a developer causes an increase of silver sludge. The thus generated silver deposit adheres to the developing tank, the rollers and other parts of an automatic developing machine, and further transfer onto photographic materials processed in the developing machine to damage their image quality.
For the purpose of decreasing such silver stain, the methods of reducing the amount of silver ion eluted and/or adding such compounds as to inhibit silver ions from being reduced to silver are disclosed in JP-A-56-24347 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-B-56-46585 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-B-62-2849 and JP-A-04-362942. Those methods suffice for the prevention of silver stain in case the developer has a reduced replenishment rate, but cannot ensure satisfactory aerial-oxidation resistance to the developer.
The addition of ascorbic acid to a developer is known. In many cases, ascorbic acid is used as developing agent, as disclosed, e.g., in U.K. Patents 956,368, 1,030,495 and 1,380,309, U.S. Pat. Nos. 3,821,000 and 2,688,549, and JP-B-36-17599. Since these patents use ascorbic acid as a developing agent and the developers used therein do not contain any hydroquinone derivatives, the effect of ascorbic acid in the present invention is away from those patents. Moreover, ascorbic acid is liable to be hydrolyzed through aerial oxidation when the amount added to an alkali developer is increased beyond 0.15 M. The hydrolysis of ascorbic acid lowers the pH of the developer to result in a lowering of the developer's activity.
The patents relating to the combined use of a hydroquinone derivative and ascorbic acid in a developer are also disclosed. For instance, there can be cited U.S. Pat. No. 3,512,981, JP-B-55-49298, U.K. Patents 1,326,495 and 1,266,533, JP-B-44-28673 and U.K. Patent 1,365,236. More specifically, these patents concern the lith type developing systems for the field of photomechanical processes. However, those developing systems are low in free sulfite ion concentration, so that their stability is poor. That is, they are undesirable from the standpoint of preservation of the developer. Further, the combined use of a hydroquinone derivative and ascorbic acid in a single bath developer is disclosed in U.S. Pat. No. 3,806,344, West German Patent 2,549,683, and so on. However, the purpose of using such developers is different from that of the present developer. The combined use of a hydroquinone derivative, ascorbic acid and a 1-phenyl-3-pyrazolidone derivative in a developer is disclosed in U.S. Pat. No. 3,865,591. The ascorbic acid used therein functions as a developing agent; moreover, the specification of the above-cited patent is silent on the effect of ascorbic acid which is revealed by the present invention. Furthermore, the developer of that patent is low in development activity because the pH range thereof is low. Therefore, it is also different in purpose from the present developer.